1. Field of the Invention
The invention relates to the detection and/or the determination of viruses by an immunoassay method, to materials for such method, and to a virus detection kit.
2. Description of the Prior Art
A number of methods are available in clinical virology which can be used to detect viruses or certain viral antigens (Ag). Infectivity assays depend upon biological amplification, i.e., the ability of viruses to multiply and provide adequate amounts for observation. In vitro methods include infection of cells for plaque formation or other readily observed cytopathic effects, whereas in vivo methods require an infection which causes the death of injected animals. These infectivity assays are accurate with respect to the presence of viable virions, but they do not directly provide viral specificity, and the procedures are tedious and time con- suming.
As indicated in Diagnostic Virology, G. D. Hsiung, Third Edition (1982), Yale University Press, New Haven and London, pages 3-6, an alternative to these methods are immunoassays which depend on the detection of a specific viral Ag by an antibody (Ab) which forms an immuno-complex with the Ag. Methods such as Immunofluorescence, Enzyme Immunoassay, and Radioimmunoassay are the three most well developed assays. They measure the presence of viral Ag, which can be the capsomere proteins of the virion, the neuraminidase and haemagglutinin "spikes" of the virion or the viral nucleic acids. These assay methods are highly specific, fast and sensitive relative to infectivity assays, but viral viability must still be verified by infectivity tests. Direct observation of virions using negative staining and an electron microscope or using immunoelectromicroscopy generally does not offer sufficient sensitivity, but has advantages of being faster than the assay methods and requiring a minimum of specimen preparation. The known assay methods have a number of limitations. Enzyme Immunoassay requires use of elaborate and costly chemistry. Radioimmunoassay involves steps requiring lengthy incubation times, and the difficulty of handling radioactive materials. Immunofluorescence methods are generally less sensitive. There is accordingly a need for a more sensitive, faster and economical method for the detection of viruses.
The method of choice, therefore, depends on the nature of the specimen, the need for rapid detection and/or high sensitivity, as well as the availability of detection instruments and reagents.
U.S. Pat. No. 3,088,875 granted on May 7, 1963 to Roy T. Fisk, discloses tests for antigens or antibodies indicative of pathological conditions, employing polymeric styrene latex having particle size of 0.15 to 0.25 micron as a carrier for specific, known antibodies or antigens. The carrier is dyed, and the presence of unknown antibodies or antigens in a specimen is determined by visual observation of flocculation of the test reagent, due to formation of immune-complexes in the mixture on a glass slide.
The introduction of tracers or labels on to microscopic particles or strands of carrier material, and use of such labelled particles in immunoassays is described in U.S. Pat. No. 3,853,987 granted on Dec. 10, 1974 to William J. Dreyer, the disclosure of which is incorporated herein by reference.
In the present applicant's copending U.S. patent application Ser. Nos. 313,711, now allowed U.S. Pat. No. 4,436,826, filed on Oct. 21, 1981 and 331,859, now allowed U.S. Pat. No. 4,454,233, filed on Dec. 17, 1981, the disclosures of both of which are incorporated herein by reference, antibody or antigen coupled microspheres having isolated tagging or labelling materials therein are disclosed for use in immunoassays. These applications also disclose use of a solid phase material which is employed for the separation of bound and free microspheres. A number of detection methods for the labelled microspheres are disclosed such as X-ray fluorescence.